[chronik] Keep required Rust version in one place

Summary: Set required Rust version on the workspace level and inherit that in all packages.

Test Plan:
mkdir buildChronik && cd buildChronik
cmake -GNinja .. -DBUILD_BITCOIN_CHRONIK=ON
ninja all check-crates
./test/functional/test_runner.py chronik_*

Reviewers: #bitcoin_abc, tobias_ruck, O1 Bitcoin ABC, Fabien

Reviewed By: #bitcoin_abc, tobias_ruck, O1 Bitcoin ABC, Fabien

Subscribers: Fabien, tobias_ruck

Differential Revision: https://reviews.bitcoinabc.org/D14378